VETERINARY researchers and practitioners from across Europe converged on Barcelona in June 2009 to discuss the challenges presented by complex enteric disorders in calves and the latest knowledge on disease control.
A two-day technical symposium – chaired by Professor Etienne Thiry of the University of Liege Faculty of Veterinary Medicine in Belgium and facilitated by Intervet/Schering-Plough Animal Health – gave more than a hundred delegates from 19 countries the opportunity to debate a variety of study reports and practical papers presented by many of the leading scientists working in the field of neonatal calf health.
The comprehensive programme covered pathogenesis of complex enteric calf disease, clinical diagnosis, epidemiology, effective prevention – through sound hygiene practices, dam vaccination and good colostrum management – and the merits of various treatment regimes.
All the speakers highlighted the multi-factorial nature of enteric disorders in calves.Akey message was that whilst infectious agents are usually the necessary causes of an outbreak of neonatal calf diarrhoea (NCD), their presence is often not sufficient to cause disease. Other factors often determine both the incidence and course of NCD.
In helping farmers manage NCD, veterinary surgeons need to focus on the things that can be changed. And without any doubt, the most important non-infectious issue is the human factor, delegates were told.
Infectious agents
Turning to the infectious agents implicated in NCD, various speakers explored the range of pathogens – namely viruses, bacteria and parasites – known to cause disease problems on European farms.
In terms of viruses, whilst rotaviruses and coronaviruses continue to represent the most common viral agents, toroviruses and calciviruses have also been implicated in calf diarrhoea outbreaks.
Delegates also heard papers on the major bacterial causes of NCD and it was pointed out that whilst bacteria continually adapt and evolve, the usual suspects are still the most relevant.
Specific E. coli pathotypes remain significant causes of neonatal diarrhoea, but Salmonella enterica serotypes, Clostridum spp and Campylobacter spp can all be involved in NCD. However, the relationship between these pathogens and their host(s) is complex and multi-factorial, with many host and bacterial determinants being involved.
In the parasite arena, it was pointed out that calves are particularly susceptible to a variety of gastrointestinal parasites – particularly the protozoa Cryptosporidium, Eimeria and Giardia. Highlighting Cryptosporidium, specifically for its under-estimated prevalence in Western Europe, a number of speakers explained that despite its high infectivity, it could be controlled through effective hygiene and treatment.
Faeces sampling and diagnosis
A series of speakers then highlighted the progress veterinarians have been able to make in terms of diagnosing NCD problems.
The development of the electron microscope wasasignificant breakthrough, delegates were told, and allowed everyone to look at faeces more closely. This led to the discovery of several viruses and in the late 1970s cryptosporidium was found in faeces samples.
Although the disease problem goes on in the intestine, faeces are the most readily available and common material available for diagnosis. However, faecal content may only partially reflect the pathogens present. Most enteric pathogens are excreted for relatively short periods and may be absent after a few days illness.
Continuing the clinical diagnostic theme, a number of papers stressed the importance of reaching an overall herd diagnosis, wherever possible, in order to recommend the most appropriate disease management regime.
NCD is very much a whole herd problem and effective diagnosis involves taking into account epidemiological considerations, results of a clinical examination and faeces sampling. A clinical examination on farm allows you to suspect any pathogens that might be implicated in the disease outbreak, but calf-side and laboratory testing of faecal samples allows confirmation of the diagnosis.
Epidemiology
Tackling epidemiology, a number of speakers focused in more detail on the NCD risk factors as well as presenting trial reports from the Netherlands, Spain and the Czech Republic. The impact of frequent calf disease on subsequent productivity was also highlighted.
It was stressed that although it was methodologically extremely difficult to demonstrate the effects of NCD on subsequent animal performance, there was considerable evidence that calf disease does cause long-lasting detrimental effects.
At first glance, the most obvious financial impact of NCD is due to mortalities, reduced weight gain during acute disease and veterinary/treatment expenses. However, reduced weight gain after apparent recovery may contribute significantly to economic losses, delegates were told.
Prevention and treatment
Addressing the important practical aspects of neonatal calf management, the symposium also focused on the care and management of the pre-weaned calf. Stressing that the birth of a calf was the culmination of a significant investment in cow care, fertility management and genetic selection, various speakers said that it was vital that newborn animals received close attention.
A calf represents the entire output of a beef suckler cow and the future for the dairy enterprise. Care of the newborn calves therefore deserves the highest priority and yet how frequently is this seen in modern farming systems?
Drawing on examples of farmer practice, the importance of dry bedding, good ventilation and a consistent supply of good quality food were highlighted. With infectious disease management, the crucial importance of colostrum and good hygiene in the prevention of NCD was also emphasised.
Although they are born with a fully functional immune system, calves have no immunity at birth because antibodies cannot cross the bovine placenta. This means that calves rely entirely on a good, early intake of high quality colostrums, preferably from vaccinated dams, to gain passive immunity from their dam.
The consensus now seems to be around four litres within the first six hours and a similar amount before the animal is a day old. Calves with an inadequate colostral status are four times more likely to die than calves with a good colostral status.
In terms of treating scour, the priorities should focus on correcting dehydration with oral rehydration therapy and IV fluids. If the calf is not severely affected, farmers should also consider feeding milk for energy to aid recovery.
Managing Cryptosporidia problems
Cryptospordium parvum is now recognised as one of the leading causes of diarrhoea in pre-weaned calves and is an increasingly common infection on many European farms. Studies have highlighted the prevalence of this infection, its economic impact and the zoonotic threat.
Prevention of cryptosporidia problems relies on good management practices. Calves should be born and reared in a clean, dry environment and should be housed in individual hutches or boxes. Healthy calves should be separated from sick calves and should be cared for by different people, using different equipment. Calf rearing areas should not be occupied continuously and should be thoroughly cleaned between batches of calves.
However, delegates were told that hygiene alone will not clear up crytopsporidia infections on problem farms. Studies in Portugal have shown the value of agent-specific drugs like halofuginone lactate (Halocur, Intervet). Provided treatment is initiated early enough (1-2 days after birth) and continued for seven days this will significantly reduce the proportion of calves suffering from cryptosporidiosis and oocyst excretion.
Vaccination
A number of speakers highlighted the value of a vaccination programme in the longer term management of NCD. In summarising the background to the development of effective vaccines, beef and dairy cow responses to vaccination to the most common pathogens causing NCD were explored.
The enhancement, by vaccination of the dam, of the passive protection provided to the young calf through the ingestion of colostrum and milk is now generally accepted as the most effective approach for protection against rotavirus, coronavirus and K99.
Vaccines, such as Rotavec-Corona (ISPAH), have demonstrated not only significant increases in the mean specific antibody titre in the serum of vaccinated animals, but an accompanying increase in protective antibodies in colostrum and milk for up to 28 days post calving.
Optimal stimulation of immunity has also resulted in a wide vaccination window offering increased flexibility to the farmer for whole herd vaccination.
Wrapping up the symposium, Dr Birgit Makoschey, global technical lead, ruminant biologicals, with Intervet/Schering-Plough, said the company was delighted to be able to collaborate with Professor Thiry to bring so many leading experts together and put them alongside practitioners to bring focus to one of the most costly disease complexes affecting the European cattle industry.
Commenting on the conclusions from the presentations and the lively panel discussions, she said: “Enteric disorders in calves continue to cost European cattle producers millions of euros, but gradually we are developing a much better understanding of the various pathogenic causes of the disease.
“And with improved diagnostic techniques now available and the development of effective vaccination and treatment regimes, clinicians are now much better placed to help calf rearers minimise the potential impact of calf diarrhoea on their units.”
